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Abstract:

Described herein is the treatment of mushrooms to enhance their vitamin D
content while preserving characteristics typically associated with fresh
mushrooms.

Claims:

1. A method for treating mushrooms, comprising: slicing the mushrooms to
produce sliced mushrooms; and exposing the sliced mushrooms to
ultraviolet radiation, at a dose level in the range of 0.02 J/cm2 to
0.2 J/cm2 and having wavelengths in the UV-B range, to produce
exposed and sliced mushrooms having an enhanced vitamin D2 content.

2. The method of claim 1, wherein the sliced mushrooms have thicknesses
in the range of 1/8 inch to 1/2 inch.

3. The method of claim 2, wherein the thicknesses are in the range of 1/4
inch to 5/16 inch.

4. The method of claim 1, wherein the dose level is in the range of 0.02
J/cm2 to 0.15 J/cm.sup.2.

5. The method of claim 4, wherein the dose level is in the range of 0.05
J/cm2 to 0.15 J/cm.sup.2.

6. The method of claim 1, wherein exposing the sliced mushrooms to the
ultraviolet radiation includes operating an UV source at a power in the
range of 1 Watt per linear foot to 50 Watts per linear foot.

7. The method of claim 6, wherein the power is in the range of 5 Watts
per linear foot to 25 Watts per linear foot.

8. The method of claim 6, wherein the UV source is a continuous UV
source.

9. The method of claim 1, wherein the ultraviolet radiation has a peak
intensity in the range of 300 nm to 330 nm.

10. The method of claim 9, wherein the peak intensity is in the range of
310 nm to 320 nm.

11. The method of claim 1, wherein exposing the sliced mushrooms to the
ultraviolet radiation is carried out for an exposure time in the range of
1 second to 35 seconds.

12. The method of claim 11, wherein the exposure time is in the range of
5 seconds to 25 seconds.

13. The method of claim 1, wherein the vitamin D2 content of the
exposed and sliced mushrooms is in the range of 400 IU to 1,000 IU per 84
g of the exposed and sliced mushrooms.

14. The method of claim 13, wherein the vitamin D2 content of the
exposed and sliced mushrooms is in the range of 500 IU to 900 IU per 84 g
of the exposed and sliced mushrooms.

15. A method for treating mushrooms, comprising: providing a source of
UV-B radiation; providing mushrooms that are oriented relative to the
source of UV-B radiation; and operating the source of UV-B radiation such
that the mushrooms are substantially continuously irradiated with UV-B
radiation, at a dose level in the range of 0.02 J/cm2 to 0.5
J/cm2 and for an exposure time in the range of 1 second to 35
seconds.

16. The method of claim 15, wherein the mushrooms are oriented such that
gills of the mushrooms face the source of UV-B radiation.

17. The method of claim 15, wherein the dose level is in the range of
0.05 J/cm2 to 0.15 J/cm.sup.2.

18. The method of claim 15, wherein the source of UV-B radiation is
operated at a power in the range of 5 Watts per linear foot to 25 Watts
per linear foot.

19. The method of claim 15, wherein the exposure time is in the range of
5 seconds to 25 seconds.

20. The method of claim 15, wherein a vitamin D2 content of the
irradiated mushrooms is in the range of 400 IU to 1,000 IU per 84 g of
the irradiated mushrooms.

Description:

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application
Ser. No. 61/051,235, filed on May 7, 2008, the disclosure of which is
incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] This invention is generally related to the treatment of mushrooms
and, more particularly, is related to the treatment of mushrooms to
enhance their vitamin D content while preserving characteristics
typically associated with fresh mushrooms.

BACKGROUND OF THE INVENTION

[0003] Fresh-cut fruits and vegetables that are ready to be used by
consumers with little or no additional processing (sometimes referred to
as "ready-to-use" produce or "value-added" produce) constitute the
fastest-growing segment of the fresh produce market. In the case of
mushrooms, appearance and cleanliness are two major factors used by
consumers in assessing the freshness or quality of the mushrooms.
Unwashed mushrooms historically have shown better long-term storage
characteristics than washed mushrooms. However, to fit the definition of
ready-to-use produce, mushrooms typically require washing to remove
surface debris prior to their use. It would be desirable to treat washed
mushrooms so as to preserve characteristics typically associated with
fresh mushrooms.

[0004] Vitamin D refers to a group of organic substances involved in
mineral metabolism and bone growth. Vitamin D can occur in various forms,
including as hormones or prohormones such as Vitamin D2 (e.g.,
ergocalciferol or calciferol) and metabolites or analogues thereof.
Vitamin D has been implicated in cancer resistance, regulation of immune
response, and prevention of disorders such as obesity. There are a
limited number of natural, dietary sources of vitamin D, such as egg
yolk, fish oil, and a few plants. Since natural diets typically do not
include adequate quantities of vitamin D, consumption of dietary sources
supplemented with vitamin D is desirable to prevent deficiencies. For
example, milk is sometimes enriched with vitamin D. With sufficient
exposure to sunlight, adequate blood levels of vitamin D can be produced
in the skin. However, vitamin D deficiency remains a major nutritional
concern in geographical areas that receive little sun, particularly
during the winter months. It would be desirable to provide a dietary
source of vitamin D and, in particular, to treat mushrooms so as to
enhance their vitamin D content.

[0005] It is against this background that a need arose to develop the
treatment for mushrooms described herein.

SUMMARY OF THE INVENTION

[0006] Embodiments of the invention include the treatment of mushrooms to
enhance their vitamin D content while preserving characteristics
typically associated with fresh mushrooms. Embodiments of the invention
also include mushrooms having enhanced vitamin D content and having
characteristics typically associated with fresh mushrooms.

[0007] Other aspects and embodiments of the invention are also
contemplated. The foregoing summary and the following detailed
description are not meant to restrict the invention to any particular
embodiment but are merely meant to describe some embodiments of the
invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a better understanding of the nature and objects of some
embodiments of the invention, reference should be made to the following
detailed description taken in conjunction with the accompanying drawings.

[0009] FIG. 1 illustrates measurements of vitamin D2 content of whole
portabella mushrooms that were exposed to ultraviolet ("UV") radiation,
according to an embodiment of the invention.

[0010] FIG. 2, FIG. 3, FIG. 4, and FIG. 5 illustrate color analysis on
sliced mushrooms exposed to UV-B radiation against controls of sliced
mushrooms that were not exposed to UV-B radiation, according to an
embodiment of the invention.

DETAILED DESCRIPTION

Overview

[0011] Embodiments of the invention relate to improvements in the
treatment of mushrooms to enhance their vitamin D content, enhance their
shelf life, provide food safety, and preserve their appearance. In
general, mushrooms that can benefit from these improvements include any
commercially available mushrooms, such as white mushrooms, brown
mushrooms, oyster mushrooms, and shitaki mushrooms, whether washed or
unwashed, and whether whole or sliced. Certain embodiments of the
invention are directed to treatment of washed and sliced mushrooms to
provide ready-to-use produce having the advantages described herein.

[0012] By way of overview, certain embodiments of the invention relate to
the treatment of mushrooms via the following operations, which are
further described herein. It should be recognized that certain of the
following operations can be omitted, combined, sub-divided, or
re-ordered. [0013] (1) Mushrooms undergo a wash process; [0014] (2)
Mushrooms are sliced; [0015] (3) Mushrooms are exposed to UV radiation;
[0016] (4) Mushrooms are cooled in a cooling tunnel; and [0017] (5)
Mushrooms are packaged and stored in a cold environment.

DEFINITIONS

[0018] The following definitions apply to some of the elements described
with regard to some embodiments of the invention. These definitions may
likewise be expanded upon herein.

[0019] As used herein, the singular terms "a," "an," and "the" include
plural referents unless the context clearly dictates otherwise. Thus, for
example, reference to an element can include multiple elements unless the
context clearly dictates otherwise.

[0020] As used herein, the term "set" refers to a collection of one or
more elements. Elements of a set can also be referred to as members of
the set. Elements of a set can be the same or different. In some
instances, elements of a set can share one or more common
characteristics.

[0021] As used herein, the terms "substantially" and "substantial" refer
to a considerable degree or extent. When used in conjunction with an
event or circumstance, the terms can refer to instances in which the
event or circumstance occurs precisely as well as instances in which the
event or circumstance occurs to a close approximation, such as accounting
for typical tolerance levels or variability of the embodiments described
herein.

[0022] As used herein, the terms "optional" and "optionally" mean that the
subsequently described event or circumstance may or may not occur and
that the description includes instances where the event or circumstance
occurs and instances in which it does not.

[0023] As used herein, the term "fresh mushroom" refers to a mushroom that
retains a set of physical characteristics substantially comparable to
those present at harvest.

[0024] As used herein, the term "freshness" refers to a condition that is
substantially comparable to that present at harvest. In some instances,
freshness can refer to a condition that is acceptable to a consumer, such
as a shopper at a retail location. Such condition can be established by
customer satisfaction surveys or by quantitative standards, such as those
set out in the Examples that follow.

[0025] As used herein, the term "substantially uncontrolled atmosphere"
refers to one in which there is a substantial absence of a control
process for respiration gases, other than that which can result from
misting or other wetting or from refrigeration. In such substantially
uncontrolled atmosphere, levels of carbon dioxide and oxygen can be
substantially comparable to levels present in the earth's normal
atmosphere, namely less than about 1% (by volume) of carbon dioxide and
about 21% (by volume) of oxygen. At a retail location for mushrooms,
surrounding conditions may increase carbon dioxide level and reduce
oxygen level to some extent, and it is contemplated that a substantially
uncontrolled atmosphere encompasses such typical variations.

[0026] As used herein, the term "modified atmosphere" refers to one in
which either of, or both, an oxygen level and a carbon dioxide level
differ from that present in a substantially uncontrolled atmosphere or
the earth's normal atmosphere. In some instances, a modified atmosphere
can include less than about 21% (by volume) of oxygen and more than about
1% (by volume) of carbon dioxide. Optional control of Relative Humidity
("RH") can include providing a relatively high RH (e.g., at or above 87%)
and the substantial absence of free liquid water (e.g., water in the form
of a mist or suspended droplets).

[0027] As used herein, the term "respiration gases" refers to either of,
or both, carbon dioxide and oxygen, the former being generated by
respiration, and the latter being consumed. Water (in the form of water
vapor) can also be generated by respiration. However, as used herein, the
control of respiration gases need not involve control over water vapor.

[0028] As used herein, the term "container" refers to any object capable
of holding or retaining another object, such as a set of mushrooms. A
container can have an internal volume larger than a volume of mushrooms
stored in the container. As such, there can be a range of relative
proportion of a "mushroom storage volume," which is a portion of the
internal volume in which the mushrooms are located when the container is
in a normal storage position, relative to a "void volume," which is a
portion of the internal volume substantially devoid of the mushrooms when
the container is in the normal storage position.

[0029] As used herein, the term "hole" refers to a channel or passageway
that permits flow of one or more of the following: oxygen; carbon
dioxide; and water vapor. A hole can be a physical opening or perforation
formed in a solid material, such as by cutting, plastic molding, or any
other suitable process, or can be a pore of a porous or semi-porous
membrane. In some instances, a hole can be formed in a wall of a
container to provide for gas exchange between an interior and an exterior
of the container.

Wash Process

[0030] Certain embodiments of the invention can be used in conjunction
with a wash process for the treatment of washed mushrooms. In general, a
wash process refers to a set of operations to substantially remove
surface debris from mushrooms after harvesting. In some instances, the
mushrooms can be subjected to an aqueous wash process using a set of
aqueous solutions, such as including a set of agents to assist in dirt
removal, preservation, bacterial suppression, or the like. An aqueous
solution can include pure water or water containing dissolved or
suspended agents used in a wash process. Other examples of aqueous
solutions include suspensions, emulsions, and other water mixtures.

[0031] An example of a wash process is described below, although it should
be recognized that other wash processes can also be used. The wash
process described herein is desirable, since it can provide preservation
characteristics in addition to washing. Further details related to this
wash process can be found in U.S. Pat. No. 6,500,476, issued on Dec. 31,
2002, the disclosure of which is incorporated herein by reference in its
entirety.

[0032] According to an embodiment of the invention, a wash process
includes: (1) contacting mushrooms with an aqueous anti-microbial
solution having a pH from about 10.5 to about 12.5, such as from about
10.5 to about 11.5; (2) contacting the mushrooms one or more times with
an aqueous pH neutralizing buffer solution that includes an organic acid
and a salt of an organic acid, wherein the solution is substantially free
from erythorbic acid and sodium erythorbate; and (3) contacting the
mushrooms one or more times with a solution that includes a browning
inhibitor and a chelating agent.

[0033] Advantageously, the wash process can be viewed as including three
distinct operational stages: (1) an anti-microbial stage; (2) a
neutralization stage; and (3) an anti-browning stage. In the first stage,
the wash process uses a high pH solution as an anti-microbial treatment
for whole or sliced mushrooms. This treatment can significantly reduce
microbial load and associated bacterial decay and browning of mushroom
tissue. To reduce damage of mushroom cap tissue from exposure to the high
pH solution, the wash process includes a neutralization stage that is
performed following exposure to the high pH solution. The wash process
also includes an anti-browning stage to address enzymatic browning. The
anti-browning stage can incorporate an anti-browning solution including
an anti-oxidant or browning inhibitor, such as calcium, to maintain
cellular tissue and to enhance browning inhibition.
Ethylenediaminetetraacetic acid ("EDTA") can be used to provide further
browning inhibition. By separating the neutralization stage and the
anti-browning stage, the wash process can be more cost effective by
reducing depletion of the relatively expensive anti-browning solution.

[0034] More particularly, the anti-microbial stage of the wash process can
involve contacting mushrooms with an anti-microbial buffer solution
having a pH from about 10.5 to about 11.5. A wide variety of compounds
can be used alone, or in combination, in this solution to attain the
desired pH, such as sodium bicarbonate, sodium carbonate, and sodium
hydroxide. In some instances, a combination of sodium bicarbonate and
sodium carbonate is desirable. About 0.3% to about 0.5% (by weight) of
sodium bicarbonate and about 0.05% to about 0.10% (by weight) of sodium
carbonate can be particularly satisfactory. In some instances, an initial
contact with the anti-microbial buffer solution can be carried out for
about 20 to about 40 seconds at an ambient temperature of about
25° C. Somewhat elevated temperatures can be used to provide
greater anti-microbial action, but these elevated temperatures can permit
lower dwell times in solution.

[0035] Next, the mushrooms can be contacted one or more times with at
least one aqueous pH neutralizing buffer solution including an organic
acid and a salt of an organic acid, while being substantially free from
erythorbic acid and sodium erythorbate. This neutralization stage is
carried out to reduce the pH of the mushrooms to a substantially normal
pH, and can be accomplished by applying the buffer solution via any
conventional techniques, such as by dipping, spraying, or cascading. In
some instances, the buffer solution has a pH of about 3.0 to about 5.0.
Acids and bases used for preparation of the salt can be weak acids and
bases, such as citric acid and sodium citrate. For example, a 0.1 N
solution of citric acid, having a pH of about 3.5, can be used
effectively. Other examples of organic acids include malic, acetic,
phosphoric, and lactic acids. Contacting time can vary, for example, with
the pH of the mushrooms after the anti-microbial stage and volume of the
buffer solution, and can range from about 10 to about 30 seconds.

[0036] The anti-browning stage of the wash process can involve treating
the mushrooms one or more times with at least one solution including a
browning inhibitor and a chelating agent. A wide variety of browning
inhibitors can be used to retard the effect of tyrosinase. These browning
inhibitors include reducing agents, such as sodium erythorbate,
erythorbic acid, ascorbic acid, and calcium ascorbate. A wide variety of
chelating agents that have a high affinity for copper can be used. These
can include, for example, polyphosphates such as sodium hexametaphosphate
and others currently approved for use on fruits and vegetables and that
are categorized by the Food and Drug Administration as Generally
Recognized As Safe ("GRAS"). Calcium disodium EDTA can also be
particularly satisfactory for certain applications. In some embodiments,
the solution used in the anti-browning stage can also include calcium
chloride.

[0037] In some instances, the pH of individual solutions can be monitored
for the purpose of maintaining an optimum pH. Also, the concentration of
sodium erythorbate can be monitored for enhancing inhibition of enzymatic
browning of mushrooms.

[0038] For certain applications, the wash process can be implemented as a
continuous process in which mushrooms are introduced into a first wash
stage and conveyed through each subsequent stage with reduced damage,
reduced browning, and reduced depletion of active ingredients. Solutions
of sodium bicarbonate and sodium carbonate can be adjusted with sodium
hydroxide to achieve a high pH in the first stage and maintained at a
temperature of at least about 25° C. After the first stage, the pH
of the mushrooms can be rapidly adjusted to about 6.5, which is more
physiologically acceptable for the mushrooms. This rapid reduction in pH
can be accomplished during a second stage of the process or as part of a
rinsing operation. The rinsing operation can occur in a tank that
contains a citrate buffer made from an organic acid and a salt of an
organic acid and that is at ambient temperature. To reduce uptake of
solution, the mushrooms can remain in the second stage for no more than
about 10 to about 30 seconds. The mushrooms can then be transported by a
conveyor to a third stage. A solution used in the third stage can be
maintained at ambient temperature and can include sodium erythorbate,
calcium chloride, and EDTA as a treatment for enzymatic browning. The
mushrooms can remain in this solution for about 20 to about 40 seconds.
The total exposure time during the three stage process can be limited to
about 50 to about 110 seconds.

Slicing of Mushrooms

[0039] Certain embodiments of the invention can be used in conjunction
with slicing of mushrooms, such as after the mushrooms undergo a wash
process. In general, slicing refers to a set of operations to cut
mushrooms after harvesting. In some instances, the mushrooms can be cut
into smaller pieces, such that an interior of a mushroom cap or stem is
exposed at a location other than an initial point where the mushroom cap
or stem was separated from a mushroom bed. Slicing of mushrooms can occur
after washing, although additional washing operations can also occur
afterwards. In some instances, slicing of mushrooms is considered to
occur after washing when at least one aqueous washing operation occurs
prior to the slicing.

[0040] Slicing of mushrooms can be performed in various ways, such as
using a grate or a Wakker slicer (Dutch Tech-Source), to produce sliced
mushrooms having a thickness of about 1/8 inch to about 1 inch, such as
from about 1/8 inch to about 1/2 inch or from about 1/4 inch to about
5/16 inch. In addition to the relatively large pieces resulting from
slicing, smaller pieces in the form of trimmings and other by-products in
the form of stumps can be subjected to further operations as described
herein.

Exposure of Mushrooms to UV Radiation

[0041] Certain embodiments of the invention can be used in conjunction
with exposure of mushrooms to UV radiation, such as after the mushrooms
undergo a wash process and slicing. In particular, it can be desirable to
irradiate the mushrooms with UV radiation so as to enhance their vitamin
D2 content. In addition, irradiation of the mushrooms with UV
radiation can provide preservation characteristics and, thereby, prolong
the shelf life of the mushrooms.

[0042] Without wishing to be bound by a particular theory, it is believed
that exposure of mushrooms to UV radiation promotes the conversion of
ergosterol within the mushrooms to vitamin D2. UV radiation that can
be used include UV-A (e.g., long wavelengths in the range of about 315 nm
to about 400 nm), UV-B (e.g., medium wavelengths in the range of about
280 nm to about 315 nm), UV-C (e.g., short wavelengths in the range of
about 100 nm to about 280 nm), and combinations thereof. For some
embodiments, UV-B, or a combination of UV-B as a substantial fraction and
UV-A as a minor fraction, is particularly desirable, since such
wavelengths are effective in enhancing vitamin D2 content, while
being safer and avoiding or reducing darkening of mushrooms that can
otherwise result when irradiating with shorter wavelengths, such as UV-C.
In particular, UV radiation with a peak intensity in the range of about
300 nm to about 330 nm, such as from about 310 nm to about 320 nm or from
about 310 nm to about 315 nm, can achieve a desired enhancement of
vitamin D2 content, while being safer from both a processing
standpoint and a consumption standpoint by avoiding or reducing chemical,
mutational, or other alterations of the mushrooms. It is contemplated,
however, that UV-C can be used in place of, or in combination with, UV-B.
In particular, UV-C is germicidal, and can be advantageously used to
provide an enhanced anti-microbial effect.

[0043] For some embodiments, a dose or energy level of UV radiation is
desirably in the range of about 0.02 J/cm2 to about 1.5 J/cm2,
such as from about 0.02 J/cm2 to about 0.5 J/cm2, from about
0.02 J/cm2 to about 0.2 J/cm2, from about 0.02 J/cm2 to
about 0.15 J/cm2, or from about 0.05 J/cm2 to about 0.15
J/cm2. Such dose level is effective in enhancing vitamin D2
content, while being safer and avoiding or reducing darkening of
mushrooms that can otherwise result when irradiating at higher dose
levels. To achieve a desirable dose level, an UV source can be
implemented as a set of rows, such as a set of rows of UV fluorescent
lamps, and each of the rows can operate at a power in the range of about
1 Watt per linear foot to about 50 Watts per linear foot, such as from
about 5 Watts per linear foot to about 25 Watts per linear foot or from
about 10 Watts per linear foot to about 20 Watts per linear foot. When
activated, the UV source desirably emits UV radiation in a substantially
continuous fashion, rather than, for example, in a pulsed fashion. Use of
such a continuous and fluorescent UV source provides a number of
advantages, including enhanced safety and greater ease and flexibility
for the treatment of mushrooms. It is contemplated, however, that a
pulsed UV source can be used in place of, or in combination with, a
continuous UV source.

[0044] Exposure time for UV radiation can be selected based on various
factors, including a desired vitamin D2 content, a dose level of the
UV radiation, and whether mushrooms exposed to the UV radiation are
sliced mushrooms or whole mushrooms. For some embodiments, sliced
mushrooms are particularly desirable, since their use can significantly
reduce the exposure time for UV radiation while achieving a desired
enhancement of vitamin D2 content for a particular dose level of the
UV radiation. A reduced exposure time can be desirable for reducing time
and cost associated with the treatment of mushrooms as well as reducing
negative impact on their appearance and undesirable alterations when
exposed to UV radiation for a prolonged period of time. Without wishing
to be bound by a particular theory, it is believed that surface area
effects provide at least some of the benefits of sliced mushrooms
relative to whole mushrooms. For some embodiments, the exposure time can
be in the range of about 1 second to about 15 minutes. In the case of
sliced mushrooms, the exposure time can be less than about 40 seconds,
such as from about 1 second to about 35 seconds, from about 1 second to
about 30 seconds, from about 5 seconds to about 30 seconds, from about 5
seconds to about 25 seconds, from about 5 seconds to about 20 seconds, or
from about 5 seconds to about 10 seconds. In the case of whole mushrooms,
the mushrooms are desirably oriented with their gills facing the UV
radiation, although at least some of the mushrooms can be oriented with
their gills facing away from the UV radiation.

[0045] Vitamin D2 content of resulting mushrooms can be expressed in
terms of quantities of International Unit ("IU"), where one IU
corresponds to 0.025 μg of vitamin D2. A serving size can be
assumed to be 84 g of the resulting mushrooms, and the current
recommended Daily Value of vitamin D2 is 400 IU (or 10 μg). For
some embodiments, vitamin D2 content of one serving size of the
resulting mushrooms can be at least a substantial fraction of the
recommended Daily Value, such as at least about 20%, at least about 50%,
at least about 80%, or at least about 90% of the recommended Daily Value,
and up to about 100% or more of the recommended Daily Value. In some
instances, vitamin D2 content of one serving size of the resulting
mushrooms can be equal to or greater than the recommended Daily Value,
such as equal to or greater than about 1.5 times, about 2 times, about 3
times, or about 10 times the recommended Daily Value, and up to about 65
times or more of the recommended Daily Value. For some embodiments, the
vitamin D2 content can be in the range of about 18,000 to about
26,000 IU per serving size when exposed to UV-B radiation at a dose level
of about 1 Joule/cm2. The resulting mushrooms can retain enhanced
levels of vitamin D2 over their shelf life. Accordingly, a consumer
can receive at least a substantial fraction of the recommended Daily
Value of vitamin D2 in a single serving of the resulting mushrooms
even at the end of their shelf life. For some embodiments, the shelf life
can be assumed to be about 10 days or less, and the resulting mushrooms
can retain at least a substantial fraction of their initial vitamin
D2 content after exposure to UV radiation, such as at least about
30%, at least about 50%, at least about 60%, or at least about 70% of
their initial vitamin D2 content. For example, the resulting
mushrooms can have an initial vitamin D2 content in the range of
about 400 to about 1,000 IU per serving size, such as from about 500 to
about 900 IU per serving size or from about 600 to about 800 IU per
serving size, so as to retain about 100% of the recommended Daily Value
of vitamin D2 in a single serving at the end of their shelf life.

[0046] In addition to enhancement of vitamin D2 content, exposure to
UV radiation can provide other improvements in terms of preserving
freshness and prolonging shelf life. In particular, over the course of
their shelf life, the resulting mushrooms can exhibit less darkening or
discoloration relative to mushrooms that are not exposed to UV radiation.
Darkening can be expressed in terms of L* parameter, which represents a
brightness parameter that extends from 0 (black) to 100 (white). For some
embodiments, the shelf life can be assumed to be about 10 days or less,
and the resulting mushrooms can retain at least a substantial fraction of
their initial brightness parameter value after exposure to UV radiation,
such as at least about 70%, at least about 80%, at least about 90%, or at
least about 95% of their initial brightness parameter value. Without
wishing to be bound by a particular theory, it is believed that exposure
of mushrooms to UV radiation can promote one or more of the following:
(1) a denaturing effect of the UV radiation on enzymes that cause
browning; (2) a direct anti-microbial effect of the UV radiation; (3)
drying of surfaces of the mushrooms during the exposure that results in
less bacterial growth and less enzymatic browning; and (4) cauterization
or sealing of the surfaces of the mushrooms.

[0047] In addition to the relatively large pieces resulting from slicing
of mushrooms, smaller pieces in the form of trimmings and other
by-products in the form of stumps can be exposed to UV radiation as
described herein. Because of their smaller size, these smaller pieces can
exhibit enhanced absorption rate of the UV radiation and enhanced
conversion rate to vitamin D2, relative to larger pieces or whole
mushrooms. When exposed to UV radiation, these smaller pieces can build
up relatively large quantities of vitamin D2, without concern for
discoloration resulting from prolonged exposure to the UV radiation. The
resulting material can be preserved through freezing or freeze drying,
and used as a flavoring additive, food additive, or dietary supplement.

Cooling, Packaging, and Storage of Mushrooms

[0048] Certain embodiments of the invention can be used in conjunction
with cooling, packaging, and storage of mushrooms, such as after the
mushrooms undergo a wash process, slicing, and exposure to UV radiation.
In particular, it can be desirable to cool the mushrooms following their
exposure to UV radiation so as to reduce any damage that might otherwise
result from the exposure and to return the mushrooms to a physiologically
desirable temperature, such as at or below ambient temperature. Cooling
of the mushrooms can be performed in various ways, such as using a
cooling tunnel or a blast cooler.

[0049] Next, the mushrooms can be packaged and stored in a refrigerated
setting, such as in a cold room or a refrigerated display at a retail
location. An example of a technique for packaging and storage of
mushrooms is described below, although it should be recognized that other
techniques can also be used. The technique described herein is desirable,
since it can extend freshness of mushrooms. Further details related to
the technique can be found in U.S. Patent Application Publication No.
2008/0093241, published on Apr. 24, 2008, the disclosure of which is
incorporated herein by reference in its entirety.

[0050] In particular, packaging and storage of mushrooms can be
implemented to provide a modified atmosphere in contact with or
surrounding the mushrooms. This modified atmosphere can involve a reduced
level of oxygen and an elevated level of carbon dioxide relative to those
present in a substantially uncontrolled atmosphere or the earth's normal
atmosphere. For example, this modified atmosphere can include an oxygen
level within a range of about 10% to about 20% (by volume), such as from
about 14% to about 18% or from about 15% to about 17%, and a carbon
dioxide level within a range of about 2.5% to about 12% (by volume), such
as from about 5% to about 9% or from about 6% to about 8%. Optionally,
this modified atmosphere can also involve controlling a RH to be in a
range of about 87% to about 100%, such as from about 88% to about 94% or
from about 88% to about 92% (in the substantial absence of free liquid
water).

[0051] A modified atmosphere can be provided in various ways. In some
embodiments, containers in the form of flexible storage bags or hard
clam-shell packagings can be used to provide the desired modified
atmosphere. This can be achieved by controlling gas flow into and out of
a container by using a set of holes, by using a set of permeable or
semi-permeable membranes, or both. In other embodiments, mushrooms can be
sold loose so that customers can select a desired amount of mushrooms.
For these embodiments, the mushrooms can be positioned in a container
with a lid that automatically closes, with a modified atmosphere being
pumped into the container from a compressed gas tank or from an
atmospheric extraction device to maintain the desired modified
atmosphere.

[0052] For example, a container can be implemented to achieve a
steady-state, modified atmosphere by providing a set of holes to control
the rate of gas exchange between an interior of the container and an
ambient atmosphere surrounding the container. An atmosphere inside the
container typically starts with normal oxygen and carbon dioxide levels
and the RH of an ambient atmosphere at which mushrooms are placed into
the container. The atmosphere inside the container then typically changes
over time as the mushrooms respire, with the level of oxygen decreasing
and the levels of carbon dioxide and water vapor increasing.
Concentration gradients can develop between the interior of the container
and the ambient atmosphere. These concentration gradients on two sides of
the holes can cause respiration gases to diffuse through the holes. In
particular, oxygen can enter to replace what has been used up by cellular
respiration, while carbon dioxide and water vapor, which have accumulated
as a result of cellular respiration, can exit. Eventually, steady-state
levels of respiration gases can be reached inside the container, with
specific levels depending on the amount of the mushrooms present to
produce and use up respiration gases and an area of the holes to allow
gas exchange.

[0053] To achieve desired oxygen and carbon dioxide levels while
maintaining a high RH in the substantial absence of free liquid water, a
container for storage of mushrooms is typically perforated. For example,
holes in the form of physical openings can be provided in a container
that would otherwise restrict water vapor movement and exchange of oxygen
and carbon dioxide with an ambient atmosphere. The holes can provide for
sufficient replenishment of oxygen and discharge of carbon dioxide to
avoid anaerobic conditions. Control of a total hole area by selecting the
number and size of the holes can allow appropriate steady-state
conditions to be reached. The desired steady-state conditions can also be
achieved by using a permeable or semi-permeable membrane in combination
with the holes.

[0054] With regard to location, size, and number of holes formed in a
container, a range of variations can be used to provide satisfactory
results in terms of a substantially even diffusion of respiration gases.
In some instances, a hole pattern can be formed in a wall or multiple
walls of a container, such that there is gas exchange between most or all
interior portions of the container and an ambient atmosphere. The holes
can be substantially uniformly spaced around the container. However, such
uniform spacing is not required in all applications. Indeed, a range of
hole patterns can be used, since diffusion of respiration gases can be
relatively rapid and can account for variations in spacing of holes. In
particular, a concentration gradient can develop to facilitate internally
generated respiration gases to diffuse to certain ones of the holes that
are located further away, while oxygen can diffuse inwardly in a similar
manner. Thus, a series of holes along a line in a wall of a container (or
along several lines spaced apart from each other) can provide adequate
uniformity of gas exchange. Such lines of holes can be relatively easy to
manufacture when the container is, for example, a flexible film storage
bag. On the other hand, holes spaced in a two-dimensional array on a
surface can also be satisfactory, and can be readily manufactured by a
number of techniques. Many satisfactory hole patterns can space a set of
holes such that a distance from any mushroom to a nearest hole is no
greater than about one third of a characteristic dimension (e.g., a
length) of a container, such as no more than about one fourth or one
fifth of the characteristic dimension. In some instances, absolute
distances between a mushroom and a nearest hole can be less than about 60
mm, such as less than about 40 mm or less than about 20 mm. These
distances can be maintained while varying a shape of a container or a
weight of mushrooms present. In the case of larger distances, specific
arrangement of interior geometry and free gas volumes (e.g., by providing
shelves in a large container to provide layers of mushrooms with spaces
between layers) can also yield satisfactory results.

[0055] In the absence of a forced exchange, gas exchange between an
interior and an exterior of a container typically occurs via diffusion.
It should be noted, however, that changing temperature and pressure can
cause some expansion or contraction of an interior volume of the
container, thereby creating conditions similar to a forced exchange. For
some embodiments, a forced-air-flow measurement technique can be used to
select a hole pattern to provide desired overall diffusion rates. An
estimate of a diffusion rate satisfactory for the practice of some
embodiments of the invention can be determined by measuring a rate of air
flow into or out of a container with a given hole pattern and under
specified pressure conditions. This flow rate can take into consideration
a weight of mushrooms that will be present in the container, as larger
amounts of mushrooms can produce larger amounts of respiration gases and,
thus, can require a larger hole area to handle a higher diffusion rate.
Using a pressure differential between an interior of a container and an
ambient atmosphere of 5 inches of water (1 inch of
water=2.49089×102 Pa), satisfactory results can be achieved
with a flow rate in the range of about 0.2 to about 0.6 Standard Cubic
Foot per Hour ("SCFH") per ounce of mushrooms, such as from about 0.3 to
about 0.45 SCFH per ounce of mushrooms. As can be recognized, SCFH is
defined relative to a Standard Cubic Foot ("SCF"), which is one cubic
foot of air at standard conditions of temperature and pressure (i.e., 1
atmosphere and 20° C.).

[0056] In some embodiments of the invention, a combination of size,
number, and location of a set of holes can be selected to achieve a
desired steady-state, modified atmosphere. In one such embodiment, a
number and size of the holes can be selected to provide from about 0.05
to about 1.5 mm2 of open area per ounce of mushrooms, such as from
about 0.08 to about 0.20 mm2 or about 0.125 mm2 (+/-10%) of
open area per ounce of mushrooms. A range of one to six holes per ounce
of mushrooms, with each hole having a characteristic dimension (e.g.,
diameter) from about 150 to about 600 μm, can be located in a set of
walls of a container. In a container designed for retail purposes, a set
of holes can be located, at least in part, in a header area away from
mushrooms to create a gradient of high to low RH. This gradient provides
desired water vapor transmission and maintains a desired RH surrounding
the mushrooms. However, a set of holes can also be located near the
mushrooms, particularly in the case of a larger container where a void
volume can be at a distance from the mushrooms at a bottom of the
container. This combination of size and number of holes per unit weight
of mushrooms (along with their location) can allow desired levels of
oxygen, carbon dioxide, and RH to develop in a void volume (e.g., a
headspace) of the container during storage. Diffusion within the
container can ensure relatively even levels of oxygen, carbon dioxide,
and RH throughout the container.

[0057] Table 1 below sets forth design parameters for containers
implemented in accordance with some embodiments of the invention:

TABLE-US-00001
TABLE 1
Hole dimension (e.g., 150-600 μm or 200-300 μm
diameter if round):
Hole dimensions (e.g., 150 × 200-300 μm or 150 × 250 μm
width × length if oblong): (max. ratio of 2.0 for length to width
ratio)
No. of holes/oz of 2-4 or 2-2.5
mushrooms:
Flow rate per hole: 0.15-0.30 SCFH at a pressure of 5 inches of
water
Flow rate per bag: 2.0-18 SCFH at a pressure of 5 inches of
water
Flow rate per oz of 0.2-0.6 SCFH or 0.3-0.45 SCFH at a
mushrooms: pressure of 5 inches of water

EXAMPLES

[0058] The following examples describe specific aspects of some
embodiments of the invention to illustrate and provide a description for
those of ordinary skill in the art. The examples should not be construed
as limiting the invention, as the examples merely provide specific
methodology useful in understanding and practicing some embodiments of
the invention.

Example 1

[0059] Effectiveness of exposure to UV-B radiation was determined by
measuring vitamin D2 content of both whole and sliced portabella
mushrooms that were exposed to UV-B radiation at different dose or energy
levels. Vitamin D2 content was measured in terms of quantities of
IU, where one IU corresponds to 0.025 μg of vitamin D2. Whole
mushrooms were exposed to UV-B radiation with gills facing the radiation
(i.e., gill-side) and with gills facing away from the radiation (i.e.,
button-side). Sliced mushrooms had a thickness of about 5/16 inch, and
were spread out in a single layer and then exposed on one side. Results
are set forth in the following Table 2. The serving size is assumed to be
84 g of mushrooms having 91.06% moisture content, and the Daily Value
("DV") of vitamin D2 is assumed to be 400 IU (or 10 μg). As can
be recognized from Table 2, both whole and sliced mushrooms exhibited
enhanced vitamin D2 content when exposed to UV-B radiation. However,
enhancement of vitamin D2 content was particularly pronounced in
sliced mushrooms, which had a vitamin D2 content in the range of
about 18,000 to about 26,000 IU per serving size when exposed to UV-B
radiation. Vitamin D2 content in the resulting mushrooms was
dependent upon dose level of UV-B radiation in the range of about 0.5 to
about 1.5 Joule/cm2.

[0060] Impact of exposure to UV-B radiation was determined by performing
color analysis on whole brown mushrooms exposed to UV-B radiation against
a control of whole mushrooms that were not exposed to UV-B radiation.
Color analysis was performed using a colorimeter, with measurements of L*
parameter, which represents a brightness parameter that extends from 0
(black) to 100 (white), b* parameter, which represents a yellow-blue
chromaticity (with positive values corresponding to intensity in yellow,
and negative values corresponding to intensity in blue), and a*
parameter, which represents a red-green chromaticity (with positive
values corresponding to intensity in red, and negative values
corresponding to intensity in green). Results are set forth in the
following Table 3. As can be recognized from Table 3, exposure to UV-B
radiation was sometimes observed to produce a darkening of mushrooms, but
the amount of darkening was relatively slight and remained relatively
constant over a 1 day interval.

[0061] Impact of exposure to UV-B radiation was determined by performing
color analysis on sliced mushrooms prior to and subsequent to the
exposure. Color analysis was performed using a colorimeter, with
measurements of L* parameter, b* parameter, and a* parameter. Results are
set forth in the following Table 4. As can be recognized from Table 4,
exposure to UV-B radiation was observed to produce a slight darkening of
mushrooms.

[0062] Impact of exposure to UV-B radiation was determined by performing
color analysis on mushrooms exposed to UV-B radiation against a control
of sliced mushrooms that were not exposed to UV-B radiation. In
particular, mushrooms were exposed to UV-B radiation as whole mushrooms,
and then sliced. Color analysis was performed using a colorimeter, with
measurements of L* parameter, b* parameter, and a* parameter. Results are
set forth in the following Table 5.

[0063] Effectiveness of exposure to UV-B radiation was determined with
respect to moisture content of whole mushrooms prior to and subsequent to
the exposure. Moisture content was expressed in terms of wet-basis ("wb")
moisture content, which represents a ratio of moisture weight to total
weight. Whole mushrooms were exposed to UV-B radiation with gills facing
the radiation (i.e., gill-side) and with gills facing away from the
radiation (i.e., button-side). Results are set forth in the following
Table 6. As can be recognized from Table 6, whole mushrooms exhibited a
reduction of moisture content when exposed to UV-B radiation. This
reduction of moisture content can prolong shelf life by inhibiting
bacterial growth.

[0064] Effectiveness of exposure to UV-B radiation was determined by
measuring vitamin D2 content of mushrooms that were exposed to UV-B
radiation. Vitamin D2 content was measured shortly after and 10 days
after exposure. Results are set forth in the following Table 7. As can be
recognized from Table 7, mushrooms were observed to exhibit a decline in
vitamin D2 content over the course of 10 days. In the case of
unwashed mushrooms and mushrooms that were washed prior to exposure to
UV-B radiation, a substantial fraction of vitamin D2 content was
retained over the course of 10 days. In the case of mushrooms that were
exposed to UV-B radiation and then washed, a greater decline in vitamin
D2 content was observed.

[0065] Effectiveness of exposure to UV-B radiation was determined by
measuring vitamin D2 content of whole portabella mushrooms that were
exposed to UV-B radiation. Vitamin D2 content was measured at
different times after exposure. The mushrooms were exposed to UV-B
radiation with gills facing the radiation (i.e., gill-side) and with
gills facing away from the radiation (i.e., button-side). Results are set
forth in the following Table 8, Table 9, and FIG. 1. The serving size is
assumed to be 84 g of mushrooms having 91.4% moisture content. As can be
recognized from Table 8, Table 9, and FIG. 1, the mushrooms were observed
to exhibit a decline in vitamin D2 content over the course of 10
days. However, retention of vitamin D2 is expected to be sufficient
over the shelf life of the mushrooms, such that a consumer would receive
at least the recommended DV of vitamin D2 in a single serving even
at the end of the shelf life. In particular, after 10 days, the mushrooms
still retained about 14,000 IU. The mushrooms were observed to lose about
40% of the initial level of vitamin D2 through the first 6 days of
shelf life, after which the decline levels off. It is expected that
sliced mushrooms would behave in a similar manner.

[0066] Effectiveness of exposure to UV-C radiation was determined by
measuring vitamin D2 content of whole mushrooms that were exposed to
UV-C radiation. The mushrooms were exposed to UV-C radiation with gills
facing the radiation (i.e., gill-side) and with gills facing away from
the radiation (i.e., button-side). Results are set forth in the following
Table 10. The serving size is assumed to be 84 g of mushrooms. As can be
recognized from Table 10, the mushrooms exhibited enhanced vitamin
D2 content when exposed to UV-C radiation.

[0067] Impact of exposure to UV-B radiation was determined by performing
color analysis on sliced mushrooms exposed to UV-B radiation against
controls of sliced mushrooms that were not exposed to UV-B radiation.
Color analysis was performed using a colorimeter, with measurements of L*
parameter (indicated as white values) and b* parameter (indicated as
yellow values). Results are set forth in the following Table 11, Table
12, Table 13, Table 14, FIG. 2, FIG. 3, FIG. 4, and FIG. 5. As can be
recognized, exposure to UV-B radiation was observed to produce an initial
darkening of mushrooms after the exposure. However, beside this initial
darkening, exposure to UV-B radiation was observed to inhibit further
darkening and other discoloration of the mushrooms relative to controls
that were not exposed to UV-B radiation. In particular, at some point
between day 4 and day 10 (which may occur during the expected shelf
life), the mushrooms that were exposed to UV-B radiation exhibited
superior visual appearance relative to the controls.

[0068] While the invention has been described with reference to the
specific embodiments thereof, it should be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted without departing from the true spirit and scope of the
invention as defined by the appended claims. In addition, many
modifications may be made to adapt a particular situation, material,
composition of matter, method, process operation or operations, to the
objective, spirit and scope of the invention. All such modifications are
intended to be within the scope of the claims appended hereto. In
particular, while the methods disclosed herein may have been described
with reference to particular operations performed in a particular order,
it will be understood that these operations may be combined, sub-divided,
or re-ordered to form an equivalent method without departing from the
teachings of the invention. Accordingly, unless specifically indicated
herein, the order and grouping of the operations is not a limitation of
the invention.

Patent applications by John S. Roberts, Honeoye Falls, NY US

Patent applications by John W. Kidder, Aromas, CA US

Patent applications by Stephen C. Lodder, Aptos, CA US

Patent applications by Tara H. Mchugh, Albany, CA US

Patent applications by AMYCEL, INC.

Patent applications in class Treatment with ultraviolet or visible light

Patent applications in all subclasses Treatment with ultraviolet or visible light